Add PyPy license and READMEs for pypy and stdlib

third_party/pypy/README.md

+Canonical versions of the files in this folder come from the
+[lib-python/2.7](https://bitbucket.org/pypy/pypy/src/23fd2966aada422b331d7d752fc383178deffb27/lib-python/2.7/?at=default)
+directory of the [PyPy repo](https://bitbucket.org/pypy/pypy).

third_party/stdlib/README.md

+Canonical versions of the files in this folder come from the
+[Lib](https://github.com/python/cpython/tree/2.7/Lib) directory of the
+[2.7 branch of the CPython repo](https://github.com/python/cpython/tree/2.7).